Jay Nixon is a lifelong resident of De Soto, Missouri, where he was born. His mother, Betty Lea (née Willson), was a teacher and president of the local school board, and his father, Jeremiah "Jerry" Nixon, served as the city's mayor. One of his paternal thrice great-grandfathers, Abraham Jonas, was an early Jewish settler in Illinois and friend of Abraham Lincoln (one of Nixon's paternal great-grandmothers was Jewish, though Nixon is Methodist).[1] His great-great-grandfather Charles Henry Jonas was the brother of Democratic U.S. Senator Benjamin F. Jonas of Louisiana and another, James Oscar Nixon, was a brother of U.S. Representative John Thompson Nixon of New Jersey. Another paternal ancestor, John Inskeep, had served as Mayor of Philadelphia (from 1800—1801 and 1805—1806).[2]

As the state's Attorney General, Nixon created the Environmental Protection Division to enforce Missouri's environmental laws. Attorneys in this division take legal action to stop the pollution of the state's air, water and soil and to look after Missouri's agricultural interests. Successful litigation by the division has resulted in the cleanup of polluted sites and millions of dollars awarded to the state. His aggressive actions in the Attorney General's Office earned him national recognition. Barrister magazine[4] named him one of the 20 outstanding young lawyers in the nation, and the Missouri Jaycees selected him one of Ten Outstanding Young Missourians. Prior to becoming Attorney General, he was recognized by the Conservation Federation of Missouri[5] for his environmental work as a state senator.

In 2013, he joined with nine mayors to establish July 15 as Social Media Giving Day, encouraging citizens to support charities via social media.[6]

On August 2, 2016, Michael Barrett, director of the Missouri State Public Defender System called on Nixon to act as a public defender in a criminal assault case. Nixon's communications director, Scott Holste, questioned the authority of Barrett to do so.[10] The appointment followed a July 2016 legal action in which Barrett et al. challenge the constitutionality of restricting funds for indigent defense.[11] In an open letter to Nixon, Barrett cites Missouri Revised Statues Section 600.042.5(1)[12] as well as the 6th and 14th amendments to the United States Constitution as reason for the controversial action. Barrett blames Nixon for the underfunding and understaffing of the public defender system and chose to appoint him because he is "the one attorney in the state who not only created the problem, but is in a unique position to address it."[13] According to Barrett, the funding for "resources that assist with delivering legal services" have increased between 5 and 6% since 2009, while costs over the same period have increased 18%. The case load has increased over 12% in the past year.[14] According to a 2008 report by the National Legal Aid & Defender Association, Missouri ranks 49th in per capita legal aid spending.[15] Ruth Petsch, Jackson County Missouri’s chief public defender, cites the lack funding for inadequate defense and 9 to 12 month delays in adjudication for indigent persons who often remain in jail and are unable to maintain active employment during that time.[16]